Method for producing a flexible electro-optic cell

ABSTRACT

Provided is a method of producing a flexible cell unit enclosed by a border seal and filled with an electro-optic material. The flexible cell includes a first and a second substrate separated by a controlled distance maintained by spacers. The method includes providing two continuous sheets of flexible plastic material to form the first and second substrates and depositing an electro-optic material on at least one substrate. The electro-optic material is non-encapsulated, non-polymeric, and contains less than 1% polymerizable material. The method also includes pairing the first and second substrates while roll-filling the flexible cell with the electro-optic material using one or more lamination rollers so that the electro-optic material completely fills the controlled distance between the first and second substrates.

BACKGROUND

Most liquid crystal (LC) devices are made from a sandwich of liquidcrystal between two spaced glass substrates coated with a transparentconductor. The glass substrates are generally held together to apredetermined gap using an epoxy-based gasket (edge seal) at the edgeand are referred to as a panel. The liquid crystal is injected into thegap of the panel using either a vacuum filling process or one dropfilling process. In the case of vacuum filling process, the gasketaround the panel is not continuous and has an opening referred to as“fill hole”. The panel is then placed in a vacuum chamber to vacate theair from within the panel. After this step, and while still undervacuum, liquid crystal is introduced to the fill hole. The liquidcrystal then fills the gap inside the panel due to capillary forces.This may be accelerated by bringing the panel to atmospheric pressureafter the liquid crystal introduction to the fill hole. The process iscompleted once the liquid crystal has filled the panel gap. However, toavoid future problems (e.g. shrinkage, formation of bubbles, etc.) theamount of liquid crystal in the panel is more than the anticipatedvolume. As such, the panels are then pressed to remove the excess liquidcrystal by a process referred to as “cold pressing”. The fill hole isthen sealed using a secondary epoxy to avoid air from entering thepanel.

This process is difficult to execute in large area panels because thefilling time is proportional to the panel area, so the waiting timeneeded for the filling to complete may take several hours for eachpanel. This process is uneconomical, especially with the additional timerequired to vacate the air in the vacuum process. Furthermore, thecontrol of cell gap becomes exceeding difficult.

The use of flexible substrates in the traditional vacuum process posesanother difficulty. When air in the chamber is vacated any trapped airin the empty cell causes the empty cell to expand, much like a balloon.This could lead to damage of the cell or breaking of the cell gasket.Extra precautions are needed, such as sandwiching the flexible cellbetween two ridged materials to prevent ballooning, for the vacuum fillprocess.

To mitigate this, a new process, referred to as one drop filling (ODF)was invented. In this process, the glass substrate is coated. A gasketis deposited around the entire perimeter of the glass substrate. Thesubstrate is then placed in a large vacuum chamber. A second glasssubstrate is also placed in the vacuum chamber and is held above theoriginal substrate. At this point, a dispenser deposits the exact amountof liquid crystal that will be needed on the bottom glass substrate.Once vacuum state is achieved, the two substrates are brought together.The epoxy gasket is cured creating a sealed system. The liquid crystalfills this panel through capillary forces. The panel can be brought toatmospheric pressure to accelerate the filling process as before. Theadvantage of the ODF method is that the cold press step is omitted.Furthermore, the system can reduce the process time, especially forlarge area panels.

An important aspect of these processing methods is that the final panelis considered to be under negative pressure. In other words, since thepanel is fabricated under vacuum, the inside pressure is considered tobe lower than the atmospheric pressure. This means that air willpenetrate the panel if given the opportunity. Therefore a breach in thegasket will result in catastrophic failure of the panel. To avoid thisproblem, the gaskets are designed to be impenetrable to air.

Glass based panels cannot be used in applications in which durability,flexibility, or light-weight is of importance. Such applications includeeyewear, protective shields, highly curved windows/displays, etc.Therefore, there is a demand for flexible plastic LC devices.

The manufacturing methods used for liquid crystal panel fabrication arenot fully compatible with plastic substrates. For one thing, plastic isflexible, making the handling of plastic substrates particularlydifficult in fabrication processes. The lack of flexibility of glasswhich is considered a drawback for many applications is in factnecessary for the fabrication processes stated above. While some smallarea plastic cells have been made using conventional processes above,the low yields have limited their introduction. This is primarily due tothe stringent conditions needed for any vacuum filling process.Furthermore, once the panel is fabricated, the plastic based deviceshave a significantly lower lifetime. This is due to the fact thatplastics are permeable materials, allowing transfer of gasses. Since thepanels are fabricated under negative pressure, air will eventually enterthe cell. This has significantly limited introduction of plastic basedliquid crystal devices. While many companies (e.g. Teijin, DuPont,Mitsubishi etc.) have been working on hard coats to reduce the gaspermeability of plastic substrates, they have not yet reached the valuesoffered by even the thinnest glass.

Some liquid crystal devices based on plastic have emerged in the market.They attempt to overcome these issues by processing the system inatmospheric pressure. A method of achieving this is to eliminate thegasket seal and use a roller to place the liquid crystal on thesubstrates. However, to avoid the liquid crystal from coming out of thepanel because of lack of gasket seal, they introduce a significantamount of polymer in the liquid crystal. In this method, the liquidcrystal material is “encapsulated,” meaning a quantity of liquid crystalmaterial is confined or contained in an encapsulating medium. Suchmicroencapsulation prevents the liquid crystal from “flowing,” makingmanufacture of large displays possible. The polymer encapsulated liquidcrystal creates micro “panels” within the large panel. The polymer alsohelps maintain the cell gap by adhering to the two substrates. Thesematerials most commonly known as Polymer Dispersed Liquid Crystal(PDLC), Nematic Curvilinear Aligned Phase (N-CAP), Polymer StabilizedCholesteric Texture (PSCT), Polymer Encapsulated Liquid Crystal (PELC),and Polymer Network Liquid Crystal (PNLC), etc. have a significantdrawback in that they do not exhibit optical clarity and are hazy due tolight scattering by the encapsulated liquid crystal domains. This haslimited their use to privacy applications (e.g. privacy windows, etc.).It should be noted that these systems lack the stability of the glasspanels because of absence of the gasket. In particular, air and moisturepenetrates the panel over time and renders the product inoperable. Assuch, these systems have not achieved marketability. To overcome thislimitation, the encapsulation size by the polymer was increased.Furthermore, patterned micropanels were created to limit the flow of theliquid crystal in the final large panel. However, these additionalstructures reduce the optical performance of the cell and createadditional effects such as diffraction. In optical device applications,a device without the presence of these polymer walls and structures areneeded to avoid any optical artifacts in the viewing area.

Other proposed solutions include, e.g., US Patent Application2009/0128771, entitled “Fabrication Methods for Liquid Crystal DisplayDevices” (Yang et al.), which describes a roll-to-roll method ofmanufacturing cells using a “patterned enclosure structure” thatincludes a plurality of stripes for dividing liquid crystals. Anothermethod uses patterned micro-polymer spacers to contain LC materialwithin small confined spaces. For example in a method described inWen-Tuan Wu et al. “P-55: Cell filling of Flexible Liquid CrystalDisplays Using One Line Filling and Tilted Roller Pressing”, SID 07Digest, p 393 (2007), micro-polymer spacers that are 10 μm wide×170 μmlong×3 μm high are formed on one substrate in order to contain theliquid crystal material in small, rectangular spaces, therefore makingmanufacture of a large cell possible. Other examples of patternedspacers include the method of Liang et al., U.S. Pat. No. 7,850,867entitled “Compositions for liquid crystal display.”

Other methods include providing a “support layer” made of a materialcapable of absorbing or binding LC material so as to make the LC layerdimensionally stable in thickness and of sufficient thickness toperform. See U.S. Pat. No. 5,868,892.

While plastic substrates lend themselves to a roll-to-roll type ofmanufacturing with reduced costs and increased manufacturing efficiency,previous efforts to implement a roll-to-roll continuous manufacturingprocess for various flexible displays have not been successful. Themanufacture of large surface area flexible displays has beenparticularly illusive. One reason is that in liquid crystal devices,such as displays or optical devices, it is essential that the liquidcrystal layer (i.e. the liquid crystal material together with any dyesmixed therein) have an optimum uniform thickness, because variations inthickness cause variations or gradations in optical properties of theliquid crystal device. In addition, the varying thickness of the liquidcrystal material will cause corresponding variations in the electricalproperties of the liquid crystal material, such as capacitance andimpedance, further reducing uniformity of a liquid crystal device,especially one with a large size. The varying electrical properties ofthe liquid crystal material may also cause a corresponding variation inthe effective electric field applied across the liquid crystal material.Additionally, in response to a constant electric field, areas of theliquid crystal that are of different thicknesses would responddifferently. Thus, there should also be an optimum spacing of theelectrodes by which the electric field is applied to the liquid crystalmaterial. To maintain such optimum thickness and spacing, rather closetolerances must be maintained. To maintain close tolerances, there is alimit as to the size of the device using such liquid crystals, for it isquite difficult to maintain close tolerances over large surface areas.In addition, the amount of liquid crystal must be controlled as is thecase in vacuum based processing. However, in a rolled based plasticprocess, the presence of vacuum is best avoided for the reasons statedabove.

For these reasons, large size single cell liquid crystal devices, suchas for example a sunroof or window, have not been made satisfactorily,mainly because of the fluidity of the liquid crystals, i.e. the tendencyof the material to flow, creating areas that have different materialthicknesses resulting in non-uniform optical and electricalcharacteristics.

Generally, it has been conventional thought that other than using thevarious encapsulation/patterned spacer methods described here, it is notpossible to make a flexible cell filled with a fluid electro-opticalmixture, such as a liquid crystal, using a roll-to-roll, roll to sheet,roll to part or continuous manufacturing process (here collectivelyreferred to as roll-to-roll). This is because of the difficulty ofworking with flexible plastics, having to maintain a controlled distancebetween the two substrates at about 5-20 μm with only a variation(tolerance) of +/−1-2 μm; the precision required to fill the controlledgap between the top and bottom substrates with an amount of liquidcrystal sufficient to fill the entire gap without forming bubbles ordefects; and the fluid nature of the liquid crystal, which requireseither having to stabilize the LC using polymerization or encapsulation,and/or having to use spacers that can form discrete patterns, all ofwhich result in “haze” which is undesirable.

Therefore, there remains a demand for an efficient manufacturing methodfor flexible, plastic, substantially polymer-free liquid crystaldevices.

SUMMARY

Disclosed herein is a continuous method of producing a flexible cellunit enclosed by a frame-like border seal, in which two flexiblesubstrates separated by a controlled distance maintained by unpatternedspacers are assembled together and roll-filled with an electro-opticmaterial (EOM) during the continuous production process. The term“roll-filled” and “roll-filling” as used herein refers to filling thespace between the flexible substrates or the active area of the cellwith the EOM using one or more lamination rollers so that theelectro-optic material completely fills the controlled distance betweenthe substrates. In some embodiments, the roll-filling is achievedwithout using vacuum (vacuum-less method).

In one embodiment, the method includes: providing two continuous sheetsof flexible plastic material to form a first (e.g. bottom) substrate anda second (e.g. top) substrate; depositing an electro-optic material onthe first substrate; using a lamination roller to mate the secondsubstrate with the first substrate and to roll-fill the cell (or sheet)with the electro-optic material so that the electro-optic material fillsthe controlled distance between the first and second substrates. Theborder sealant may be applied before the step of depositing the EOM orafter the EOM has been deposited.

In some embodiments, a border sealant is applied before the roll-fillingstep, so the method includes the step of applying a border sealant onthe first and/or the second or both substrates before depositing theEOM, and a step of curing the border sealant to form the border sealbefore or after the roll-filling step. In this method, the electro-opticmaterial can be deposited on an area outside the perimeter of the bordersealant (FIG. 3A). Alternatively, the electro-optic material can bedeposited inside the perimeter of the border seal (FIG. 3B). In otherembodiments, the EOM may be deposited both outside and inside theperimeter formed by the border sealant, in one or a variety of shapes.(FIG. 3C-F). This method can have a further step of cutting the flexiblecell unit from the two continuous sheets of flexible plastic materialusing a mechanical cutter (e.g. a xy-cutter or die cutter), or a lasercutter, or a combination thereof, or any other cutting/separationtechnique known in the art.

It may be advantageous in some cases for the border sealant to beprinted on both the top and bottom substrates. In this embodiment,during the roll-filling process EOM flows between the top and bottomborder sealants rather than strictly over the bottom border sealant.This ensures that the border sealant has contact to each substratesurface. This promotes adhesion and stability of the seal.

In some cases, more than one border sealant may be applied, e.g. two ormore types of adhesive may be employed to provide the border seal, eachadhesive providing a different functionality, e.g. an adhesive functionvs. a non-interacting function.

In other embodiments, the EOM is applied first, then the border sealantis applied and the cell is roll-filled. In one embodiment, the bordersealant is cured before the roll-filling step. In another embodiment,the border sealant is cured after the roll-filling step.

When a border sealant is present, it has a viscosity>1000 centipoise(cP), >2000 cP, >3000 cP, >4000 cP, or >5000 cP. In some embodiments,the viscosity is less than 10,000 cP, 20,000 cP, 30,000 cP, 40,000 cP,50,000 cP, 60,000 cP or 70,000 cP. In some embodiments, the ratio of theborder seal viscosity to EOM viscosity is greater than 5, 6, 7, 8, 9,10, 20, 30, 40, or 50.

In some embodiments of this method, the electro-optic material does notchemically interact or interacts only minimally with the border sealant.In some examples, multiple (i.e. more than one) border sealants may beapplied to one or both substrates.

In another embodiment, a border seal is created after the roll-filingstep using a laser or heating element or similar welding method used toseal around the roll-filled cell. The laser is able to melt the top andbottom substrates together to form a continuous seal around an activearea. The laser can also be configured to simultaneously cut anindividual cell from a sheet while creating the seal. The steps in thismethod include: providing two continuous sheets of flexible plasticmaterial to form the first (bottom) substrate and the second (top)substrate; depositing an electro-optic material on the first (or second)substrate; using a lamination roller to mate the second substrate withthe first substrate to form a cell filled with the electro-opticmaterial and having a controlled distance maintained by unpatternedspacers; then laser cutting a shape to form a border seal and toseparate the flexible cell unit from the two continuous sheets offlexible plastic. In this method, a border sealant is not applied beforethe roll-filling step. Rather, the border seal is created after theroll-filling step.

In any of the methods described above, the sheets of flexible plasticmay be pre-coated with unpatterned spacers, or the process can furtherinclude a step where the unpatterned spacers are applied onto the firstsubstrate, or the second substrate, or both. In yet other embodiments,the spacers may be deposited within the electro-optic material. Or,alternatively, the spacers may be deposited within an alignment layer onthe first substrate, the second substrate, or both.

In some examples, the spacers may be printed onto one or bothsubstrates. The distribution of the spacers must be such that theyproduce only minimal or no diffraction patterns. Therefore the term“unpatterned spacers” refers to spacers with a random or anon-diffraction producing pattern.

Moreover, in most examples described herein, the spacer count (ordensity of the spacers) is kept at >80 per square mm.

In any of the embodiments described above, the substrates may include aconductive layer (e.g. indium tin oxide or ITO) for application of avoltage or electric current to the electro-optic material. Accordingly,the sheets of flexible plastic may be pre-coated with a conductivelayer, or the process can further include a step where conductive layeris applied to the first and second substrates.

The first and second substrates may also include an alignment layer toassist with alignment of the EOM molecules. The alignment layer mayalready be present on the continuous sheets of flexible plastic material(pre-coating). Alternatively, the method may include a step ofdepositing the alignment layer on the first substrate, the secondsubstrate, or both. The alignment layer may be applied to the entiresurface of the first or second substrate sheets, or applied selectivelyto a selected active area on one or both first and second substrates.Active area refers to the area on the substrate that is to be filled bythe electro-optic material and bordered by the border seal. Selectiveapplication may be achieved using various techniques, for example,screen printing, inkjet printing, planar coating, roller pressing,thermal pressing, phase separation out of a mixture or other methodsknown in the art. In some cases this is a self assembling monolayer thatcan produce a desired alignment.

In some embodiments, the alignment layer may contain spacers thatmaintain the controlled distance between the substrates.

The electro-optic material includes any material that can be altered bythe application of an electric current or voltage. Examples includeliquid crystals, electro-chromic materials, SPD etc.

In some embodiments, the electro-optic material as a whole is notpolymerizable and non-encapsulated or does not contain more than 1%, 2%,3%, 4%, 5% polymerizable material. In some examples, the electro-opticmaterial includes a non-polymerizable, non-encapsulated liquid crystal,or a liquid crystal-dye mixture. In some examples, the electro-opticmaterial is a guest-host dichroic dye-liquid crystal mixture. In someexamples, the EOM is non-discrete. In other embodiments, especiallywhere the flexible cell is large, the EOM may be divided/partitionedinto discrete areas by application of partition walls in addition tounpatterned spacers, to assist in maintaining the controlled distancebetween the substrates.

The electro-optic material can be deposited in drops, lines or shapes orsheets in continuous film on the first substrate using any depositionmeans known in the art. (FIGS. 3-5)

When the EOM contains a liquid crystal mixture, the substrates can becoated with an alignment layer and the method can include a step oftreating the alignment layer to allow proper alignment of liquid crystalmolecules (and/or dye) with the substrates. “Treated,” as used here,includes any number of ways known in the art to produce a desiredalignment of the liquid crystal. For example, the alignment layerpolyimide (PI) could be physically rubbed with a soft cloth.Alternatively, while the PI is drying it could be aligned with air jets.Also known are photo-alignable alignment layers that induce alignmentwith UV light, etc.

In some embodiments, the flexible cell unit is an optical device. An“optical device” refers to a device having optical properties suitablefor a user to be able to look through the device without significantdistortion of the image seen through the device. An optical device,then, is distinct from a traditional display, because typically a userdoes not look through a display at an image. Examples of optical devicesinclude glasses, goggles, visors, protective eyewear, sunroofs, windows,fenestrations, etc. In some examples the optical device has a haze valueless than 15%, 10%, 7%, 5%, 3%, 2% or 1%.

In some examples, the flexible cell unit is an optical device containinga liquid crystal-dichroic dye mixture capable of switching between ahigh transmission “clear” state and a low-transmission “dark” state withapplication of different voltages. Such guest-host liquid crystal-dyemixtures are well suited to the manufacturing method disclosed hereinbecause of the cell's relatively higher tolerance for variations in thecell gap.

One of the many advantages of the inventive method described herein isthat it can be performed as a vacuum-less method. But it can also beperformed under vacuum, if required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view of a flexible cell unit.

FIG. 2 is a schematic diagram of an embodiment of a roll-fillingfabrication method of a flexible cell unit where the border sealant isapplied before the roll-filling step.

FIGS. 3A-F are schematic views of various examples of the placement ofthe EOM in relation to the border seal during a roll-filling process,showing examples of various EOM deposition patterns.

FIG. 4 is a schematic view of another embodiment of a roll-fillingmethod where the border seal is created after the roll-filling step.

FIGS. 5A-C show examples of various EOM deposition patterns that can beused with the method shown in FIG. 4.

FIG. 6 is a schematic view of an example of a single roller roll-fillingmethod.

FIG. 7 is a schematic view of an example of a double roller roll-fillingmethod.

FIG. 8 is a schematic view of an example of a vertical roll-fillingmethod.

DETAILED DESCRIPTION

Disclosed herein is a method of producing a flexible cell unit enclosed(edge sealed) by a border seal and filled with an electro-optic material(EOM). Generally, the method includes providing two continuous sheets offlexible plastic material to form the first (e.g. bottom) substrate andthe second (e.g. top) substrate; depositing or dispensing a quantity ofan electro-optic material on the first substrate; and using a laminationroller to (a) mate the second substrate with the first substrate and (b)to roll-fill the cell with the electro-optic material so that theelectro-optic material fills a controlled distance between the first andsecond substrates.

FIG. 1 is a schematic diagram of a flexible cell unit 10. The cell 10includes top and bottom flexible plastic substrates 12, 14,respectively. Depending on the application, the substrates may be coatedwith a conductive layer 16. Optically clear conductive layers includeIndium Tin Oxide (ITO), conductive polymers, conductive nanowires andthe like. Alternatively or in addition, the substrates may also becoated with an alignment layer 18, such as a polyimide or the like.

The flexible substrates 12, 14 are made of clear flexible plasticssuitable for constructing flexible cell units such as polycarbonate(PC), polycarbonate and copolymer blends, polyethersulfone (PES),polyethylene terephthalate (PET), cellulose triacetate (TAC), polyamide,p-nitrophenylbutyrate (PNB), a polyetheretherketone (PEEK), apolyethylenenapthalate (PEN), polyetherimide (PEI), polyarylate (PAR);or the like as known in the art. Many of these substrates arecommercially available from e.g. Mitsubishi Plastics or Teijin DuPontfilms and come standard with various coatings such as hard coats.

The flexible substrates 12, 14 are separated by a controlled gap ordistance, which is maintained by spacers 24. The volume between thesubstrates is filled by an electro-optic material 26.

The spacers 24 are used to maintain a controlled distance or gap betweenthe substrates. In some embodiments, the controlled gap is 3, 4, 5, 6,7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 30, 40, 50, 60, 70,80, 90, or 100 μm in size. In some examples, the controlled gap ispreferably 5, 6, 7, 8, 9 or 10 μm, in size. A “controlled” gap ordistance means the variation in the distance between the substratesshould remain on the average less than 30% of spacer diameter (whichdetermines the controlled gap). In some examples, the variation is lessthan 25%, 20%, 15%, 10% or 5% of the spacer diameter.

Generally, two kinds of spacers are used to maintain a controlleddistance between substrates. One category are “patterned spacers”, whichare spacers that are either purposefully placed or created on asubstrate to form a particular pattern of repeated geometry, or they arecreated using a photolithography/polymerization or similar method knownin the art and which produce a diffraction pattern. Examples includepolymer walls. Other examples include the patterned spacers used inWen-Tuan Wu et al. “P-55: Cell filling of Flexible Liquid CrystalDisplays Using One Line Filling and Tilted Roller Pressing”, SID 07Digest, p 393 (2007). Wu et al., uses a photolithography technique toform patterned micro-polymer spacers (10 μm wide×170 μm long) that areelongated to create long rows of liquid crystal. Typically, thesespacers have a length and width that are larger than the cell gap, i.e.,they possess an aspect ratio of long side to cell gap that is >20 in apattern that can produce visible patterns in the device.

In contrast to the above, the present method uses “unpatterned spacers”to maintain the controlled distance between the substrates. “Unpatternedspacers”, as defined herein, are spacers that are placed randomly (e.g.sprayed on) or printed where they are positioned in a way so as not toproduce optical aberrations such as diffraction patterns, etc. Theunpatterned spacers of the present application can be spherical or theycan be oblong with an aspect ratio (length/width) less than 10/1 or 5/1,4/1, or 3/1. The spacers are used to maintain a distance between thesubstrates of 3-100 μm, preferably 4-20 μm.

Another distinction of the method described here is that the spacercount or density. The method works well when the substrates are coveredwith a greater density of smaller spacers than when long patternedspacers are placed in select locations. For example, in someembodiments, the spacer count is kept at >80 per square mm (mm²).

In some embodiments, the spacers 24 may be pre-applied to the substrates(e.g. the continuous sheets are pre-coated with spacers) or may beapplied to the substrates during the roll-to-roll process, for examplesprayed on or applied in a layer where the spacers are randomly arrangedor are arranged in a non-diffraction-producing pattern. They may bedispersed using a wet or dry method as known in the art. They may alsobe placed within the alignment layer, during a pre-coating process orduring the roll-to-roll manufacture process. The spacers may also becoated with an adhesive layer.

Spherical spacers are distinct from the spherical encapsulated liquidcrystals such as those described in FERGASON, Patent Application of,PCT/US1982/001240 (WO/1983/001016) entitled: “Encapsulated LiquidCrystal and Method”, because they do not encapsulate any volume of theEOM.

In certain embodiments, the spacers 24 can be deposited inside or aspart of the alignment layer, so that they are applied when the alignmentlayer is applied to one or both substrates. In other embodiments, thespherical spacers 24 can be integrated into the electro-optic materialthat is deposited onto the substrates.

The cell 10 further includes a border seal (edge seal) 27/28, whichcontains the EOM inside the cell and forms a barrier between the outsideenvironment and the EOM, preventing the EOM from flowing out of the cellas well as preventing environmental factors (air, moisture, debris) fromgetting inside the cell. In some examples, the border seal is formed byapplying a border sealant to one or both of the substrates, which whenbrought together and cured, will form the border seal around theelectro-optic material contained within the cell. FIG. 1 shows thevariation in the border seal depending on the various coatings on thesubstrates when the border sealant is applied. In FIG. 1, on one side,border sealant 27 seals the flexible substrates 12, 14 together.Alternatively, the border seal arrangement can be as pictured on theother side of the cell with border sealant 28 sealing the gap betweenthe alignment and/or conductive layers. The particular arrangement willdepend on the timing and method of the border sealant application

In some embodiments the border sealant has a viscosity less than 70,000cP and greater than 1000 CentiPoise (cP), 2000 cP, 3000 cP, 4000 cP, or5000 cP during the roll-filling process. This includes thermal adhesivesthat decrease in viscosity when heat is used to assist the bonding, aswell as thixotropic adhesives, that change viscosity in response topressure. In some embodiments, the ratio of the border seal viscosity toEOM viscosity is greater than 5, 6, 7, 8, 9, 10, 20, 30, 40, or 50. Insome examples, a border seal with a viscosity of 6000 cP has been usedsuccessfully. The viscosity of the border sealant affects the integrityof the cell because if the viscosity of the border sealant is too low,it can mix with the EOM during processing promoting a chemicalinteraction or flowing with the liquid crystal during the roll fillingprocess and depositing on the substrate's surface in undesiredlocations. If the border sealant is too viscous, the controlled gap ordistance around and close to the border seal are not uniform.

In some examples, it is advantageous if the border sealant materialexperiences minimal or no chemical interaction with the electro-opticmaterial 26 over a long period of time, typically more than 6 months,more than 1 yr, more than 2 yrs, etc. For example, we found that overtime (e.g. six months or greater), the sealant can deteriorate orinteract with the electro-optic material (e.g. liquid crystal) insidethe cell to form micro-pores that allow air to creep into the cell, thusforming bubbles or imperfections. In some examples, it is advantageousif the border sealant is non-porous to the EOM or its components. Forexample, we found that porous border sealants reduce the life time ofthe device by adsorbing some of the EOM components. Some boardersealants have exhibited chemical interaction in the form of unwanteddiscoloration of the liquid crystal near the border seal. In someinstances of chemical interaction the border sealant itself becomesdiscolored. These interactions are undesirable.

The border sealant can be applied using any technique known in the art,such as a e.g. using brushes, rollers, films or pellets, spray guns,applicator guns, screen printing, inkjet printing, flexographicprinting, planar coating, roller pressing, thermal pressing, etc. All ofthese can be done manually or can be automated into a machine, or acombination thereof. The border sealant can be a suitable adhesive (UV,thermal, chemical, pressure, multi-part epoxies, and/or radiationcured), polyisobutylene or acrylate-based sealants, and so on, or apressure sensitive adhesive, a two-part adhesive, a moisture cureadhesive, etc. Other types of border (edge) seal can be composed ofmetallized foil or other barrier foil adhered over the edge of the cell.It has been found that hybrid radiation and thermal cure sealants (i.e.UV curable with thermal post-bake) offer certain advantages. Forexample, Threebond 30Y-491 material (from Threebond Corporation,Cincinnati, Ohio) is especially useful because of its favorable watervapor barrier properties, low viscosity at elevated temperature for easydepositing of the edge seal material, good wetting characteristics, andmanageable curing properties. Those skilled in the art and familiar withadvanced sealants will be able to identify other sealants that offercomparable performance.

The cell 10 is filled with an electro-optic material (EOM). Theelectro-optic material can be any material that is responsive to anelectric field applied across the cell so as to have a desired operatingcharacteristic intended for the device, and includes any material thatcan be altered by the application of an electric current or voltage. Forexample, the EOM may be one or a combination of a liquid crystalmaterial, an electro-chromic material, a suspended particle device(SPD), with other additives such as dyes (dichroic dyes, pleochroicdyes, etc.), and the like, where the electro-optic material can bealtered by the application of an electric current or voltage. In apreferred embodiment, the EOM is a guest-host liquid crystal-dichroicdye mixture.

In some embodiments, the electro-optic material as a whole is notpolymerizable, non-encapsulated and non-discrete. Thus, the EOM materialexcludes polymeric or encapsulated liquid crystal compositions such asPDLC, PELC, PSCT, PNLC, NCAP, etc.

As used herein, “not polymerizable” means an EOM composition that doesnot include any chemical components (e.g. polymer) in an amountnecessary to dimensionally stabilize the EOM layer by changing the phaseof the material to a solid, a semi-solid, or a gel, etc.

“Non-discrete” means an EOM that is not divided into discrete, separatecompartments by encapsulation, polymer walls, polymer networks,patterned spacers, or the like.

“Non-encapsulated” means an EOM that is not contained within theconfines or interior volume of a capsule. A capsule refers to acontainment device or medium that confines a quantity of an EOMmaterial, such as a liquid crystal, so that an “encapsulated EOM” is aquantity of EOM confined or contained in an encapsulating medium, e.g. apolymer capsule. The capsules may have a spherical shape, or may haveany other suitable shape. Encapsulated EOM (e.g. encapsulated liquidcrystals) are made to prevent them from flowing. Examples ofencapsulated EOMs include: polymer-dispersed liquid crystals (PDLCs),which consist of droplets of liquid crystals inside a polymer network.

“Roll-to-roll process” means the entire process the substratesexperience, from unwinding from their corresponding roll to manufactureof a cell.

For example, a method of microencapsulation is described by FERGASON inU.S. Pat No. 4,435,047 entitled: “Encapsulated liquid crystal andmethod” (1984) and in Patent Application PCT/US1982/001240(WO/1983/001016) entitled: “Encapsulated Liquid Crystal and Method.” Inthis method, a resin material is used to encapsulate the liquid crystal(LC) material to form curved, spherical capsules containing discretequantities of LC material. These are made by mixing together LC materialand an encapsulating medium (e.g. resin) in which the LC material willnot dissolve and permitting formation of discrete capsules containing LCmaterial. In the micro-encapsulation, the liquid crystal is mixed with apolymer dissolved in water. When the water is evaporated, the liquidcrystal is surrounded by the polymer. A large number of tiny “capsules”are produced and distributed through the bulk polymer. Materialsmanufactured by encapsulation are referred to as NCAP or nematiccurvilinear aligned phase.

There are other methods of preparing PDLCs, PSCTs, PNLC such as phaseseparation, e.g. Polymerization Induced Phase Separation (PIPS). WithPIPS, droplets of LC are excluded from the bulk via phase separation aspolymeric chains grow in molecular weight—the LC becomes encapsulatedinto micron-sized droplets by solid polymer walls. Once encapsulated,the liquid crystal cannot flow between the substrates or leak out if thesubstrates are cut. This method is described in, for example, Schneideret al., SID Int. Symp. Digest Tech. Papers, vol. 36, p. 1568 (2005); andSchneider t. “New Developments in Flexible Cholesteric Liquid CrystalDisplays” Emerging Liquid Crystal Technologies II, Proc. of SPIE, Vol.6487, 64870J (2007).

When the electro-optic material includes a “guest-host” liquidcrystal-dye mixture, the mixture includes a quantity of one or moredichroic dye “guests” mixed inside a liquid crystal “host” solution. Theliquid crystal “host” molecules have an axis of orientation that isalterable by adjustment of a voltage applied across the substrates. The“guest” dye mixture includes one or more dichroic dyes which aredissolved within the liquid crystal host, align with the orientation ofthe liquid crystal molecules and whose absorption of polarized lightstrongly depends on the direction of polarization relative to theabsorption dipole in the dye molecule. An applied voltage results in aswitch between a first state, where the guest-host orientation allowsmaximum light transmission, referred to here as the “clear state”, and asecond state, where the guest-host orientation allows minimum lighttransmission, referred to here as the “dark state”, and a combination ofintermediate states, between the fully clear and fully dark states.Depending on the composition of the guest-host mixture, the clear statecan occur at zero voltage (Off state). Alternatively, the mixture may beformulated so that zero voltage (Off state) corresponds to a dark (min.transmission) state.

Cells containing guest-host liquid crystal-dye mixtures are particularlywell-suited for manufacture according to the methods described hereinbecause of their greater tolerance for variation within the cell gap,i.e. the cell is more forgiving and can function well even if the cellgap has slight variations (within acceptable limits such as +/−5%, 10%,15%, 20%, 25% or even 30%) as compared with cells relying on phaseretardation, such as polarizer-based LC devices, where the tolerance orvariation in cell gap has to be kept to <1%.

In some embodiments, the guest-host liquid crystal-dye mixturesdescribed above are used to attenuate light in an optical device. An“optical device” refers to a cell which is a primarily transmissivedevice through which users can see objects (e.g. a pair of glasses,goggles, visors, or a window).

A device having a clear (maximum transmission) state at zero voltage(Off state) can be achieved, for example, where the guest-host liquidcrystal-dye mixture has a homeotropic alignment (i.e. perpendicular tothe substrates) when no voltage is applied, the liquid crystal host hasnegative dielectric anisotropy and the dichroic dyes have positivedichroism (i.e. having maximal absorption when the polarization isparallel to the long molecular axis of the dye molecule and a minimalabsorption when the polarization is perpendicular to the long axis). Insuch a device, when upon application of a voltage (ON state), theguest-host mixture assumes a planar or homogeneous alignment (i.e.parallel to the substrates) and becomes maximally light absorbing(dark). Such an arrangement can be used in, for example, goggles,eyewear, visors, etc., where it may be desirable to “darken” the devicein response to a voltage applied when there is bright light. Otherapplications include windows (vehicles, buildings, aircrafts, etc.) andsun/moon roofs, etc.

In other examples the reverse alignment can be implemented so that theguest-host liquid crystal-dye mixture can have a planar alignment(homogeneous) in a dark state, when the applied voltage is OFF, and ahomeotropic alignment in the clear state when voltage is applied. Thiscan be achieved by use of a planar surface treatment for the alignmentlayers in conjunction with a dye having positive dichroism and a liquidcrystal material with positive dielectric anisotropy. Such anarrangement may be used in, for example, a window or sunroof, where itis desirable for the device to be normally in a “dark” state, butcapable of switching to a clear state by application of a voltage.

Finally, the cell 10 may be connected to a control circuit 30 forapplication of an electric field or voltage across the cell. The voltagesource may be either AC or DC.

One example of a roll-filling method for making cell 10 is illustratedin FIG. 2. In this example, two rolls of flexible plastic 100, 102, areused to form a top substrate 104 and a bottom substrate, 106,respectively. The continuous sheets of plastic are placed onto sets ofrollers (108) that rotate and move the plastic sheets towards a set oflamination rollers 110, 110′. In this example, each continuous sheet offlexible plastic is previously coated with an ITO conductive layer. Aset of applicators 112, 112′ is used to apply a polyimide alignmentlayer 116, 116′ onto the top and bottom substrates 104, 106. A sprayapplicator 117 is used to apply a layer of spherical spacers 118 ontothe bottom substrate 106.

FIG. 2 shows the spacers being applied to the bottom substrate, but inother examples, the spacers may be applied to the top substrate, or toboth the top and bottom substrates. Spacers may be applied to a singleor both rolls of substrate before the roll-to-roll process. Spacers 18may also be applied during the roll-to-roll process using any methodknown in the art, including wet or dry spraying, nebulizing, printing orwet coating in solution.

In some examples, the spacers may be embedded in and applied as part ofthe alignment layer. In yet other examples, the spacers may be embeddedin and applied as part of the EOM when the EOM is deposited onto asubstrate.

A screen printer 119 prints a border sealant pattern 120 on the bottomsubstrate 106 as the substrate rolls in direction A. In some embodimentsthe screen printer is a rotary screen printer and the top substrate,bottom substrate or both top and bottom substrates are printed with aborder sealant.

A strip or line of an EOM such as a liquid crystal/dye mixture 124 isdeposited onto the bottom substrate 106 close to but outside the areaformed by the border sealant 120, using a depositing needle 125. Alsocontemplated herein is a method where the EOM 124 is deposited beforethe border sealant 120.

The lamination rollers 110, 110′ are then used to bring together and“mate” the top substrate 104 and the bottom substrate 106, while thepressure from the rollers pushes the EOM 124 to roll over the borderseal 120 and into the “active” area inside the perimeter of the bordersealant 120, thus forming a cell 130 filled with the EOM 124. The“mating” of the top and bottom substrates brings the top substrate 104into contact with the border sealant 120, and into contact with spacers118, which separate the top and bottom substrates by the width of thespacers. The spacers 118 maintain a controlled distance or “gap” betweenthe top and bottom substrates, which in turn is filled with the EOM 124.

Finally, the border sealant 120 is cured by a curing apparatus 128 andthe cell 130 is cut and removed from the rolling plastic sheets.However, it is possible to first cut and separate the cell and then curethe border seal using UV light, heat, pressure, chemical interaction,moisture, or a combination thereof, or any means for curing the bordersealant. Sections of mated substrates, containing cells, can be cut intosheets contain cells. The cells can then be cut out by other methodseither mechanically or optically. Mechanical means include die cutting,cutting with an x-y razor blade, or scissors, etc. Optical cuttingincludes laser cutting, etc.

The electro-optic material can be deposited on either the inside or theoutside of the perimeter of the border seal, as shown in FIG. 3A-3B. Inother examples, the EOM may be deposited in various areas both insideand outside the border sealant (FIGS. 3C-3F). The electro-optic materialcan be selectively deposited in drops, lines, or shapes, as shown inFIG. 3.

If part or all of the EOM is deposited outside the border sealantperimeter, pressure from the lamination roller causes the EOM to rollover the border sealant in order to fill the active cell area.Therefore, it is preferable to have minimal interaction between theelectro-optic mixture and sealant so one does not interfere with thefunction of the other.

Border-Less Processing

In another embodiment of the method of manufacture, shown in FIG. 4, noborder seal is applied before the roll-filling step. Rather, a quantityof an EOM 270 is applied onto a substrate 272, then the two substrates272, 274, which have been pre-coated as desired, are brought togetherand roll-filled with the EOM, their separation maintained by spacers onone or both substrates. The step of roll-filling may be performed by asingle or by double rollers.

An edge seal 278 is created by a laser-cutting or laser-weldingapparatus 279 which acts to cut a shape and create a border seal at thesame time, and an EOM-filled flexible cell unit 280 is created andseparated from the remainder of the continuous sheet of plastic.Alternatively, a two step method may be employed where the substratesare first welded together without separating the cell from the matedsubstrates, and then the cell is cut and/or separated from the remainderof the sheet. The welding step can be performed with a laser, heat, or acombination of both.

FIGS. 5A-C show various patterns of EOM deposition in the border-lessmethod shown in FIG. 4. As can be seen, the EOM s deposited in discretepatterns or as a “sheet” covering most of the area on one (or both)substrates.

Any of the methods described herein can be used to manufacture largearea devices, i.e. anything having an area greater than 30 cm², 40 cm²or 50 cm²; or any cell over 10 cm long.

In some embodiments, the process is performed without using a “filmguider”. A “film guider” is a rigid sheet used to guide, usually the topsubstrates, into the proper alignment. Such a top film guider isdescribed in Wu et al. “P-55: Cell filling of Flexible Liquid CrystalDisplays Using One Line Filling and Tilted Roller Pressing”, SID 07Digest, p 393 (2007). However, its use has the disadvantage that such a“guider” can easily touch and scrape the top substrate, thereforescratching it or scraping off coatings such as the conductive and/oralignment layer.

The method described herein can also be implemented without using a“plate” to carry one or both substrates. For example, in Wu et al., thebottom substrate is fixed to a “stage” or a plate. This plate can be thelimiting factor in the size of the cell manufactured. In order to createa large cell (e.g. display, window), a large plate is needed. This takesup valuable space in a clean room environment. Additionally, eachdifferent sized cell would require a different size plate. Moreover,using a stage to move the substrate is problematic in large flexiblecell manufacture because the gap between the substrates needs to bemaintained constant, with a low variation (e.g. tolerance of +/−15% or1-3 μm) for the cell to operate correctly. But the stage itself is oftennot completely flat, so with larger cells, it becomes increasinglydifficult to maintain such a low tolerance.

When the roll-filling method described here does not use a plate orstage, the movement of the plastic substrates is made possible by themovement of the rollers. Therefore, the method can be adapted to createvarious size cells rapidly and easily. For example, one length cell canbe made and the very next cell can be a different length, with noretooling steps and no material waste.

The mating (lamination) step between the two substrates can be achievedusing one or two rollers. When using two rollers, the pressure and orgap between the two rollers is used to laminate the two substrates. Therollers can be made from rubber, metal or a combination thereof where,for example, one roller has a rubber and the other roller has a metalouter layer. It is well known in the art that in roll-to-rollfabrication, the diameter of the roller and plastic strength must betuned to avoid damage.

When the lamination is achieved using a single roller, the tension inthe web is the primary source of pressure. In one example, the twosubstrates are allowed to move around a roller, each, and the laminationpressure is achieved due to the tension on the roll.

The substrates may be prelaminated to a protective film for protectionagainst scratches from the process, or to increase its thickness oralter the tensile strength. Further, the substrates may be pretreated byfunctional coatings such as antifog, antireflection, hardcoats, sliplayers etc.

In the examples below, we describe how a flexible liquid crystal cell ismanufactured according to the method described herein.

EXAMPLE 1

-   -   Two substrates pre-coated with ITO and alignment layer PI are        placed on a set of rollers, one to form a top substrate and the        other forms a bottom substrate    -   Bottom substrate is sprayed with unpatterned spacers,    -   A border sealant is printed onto the bottom substrate    -   A line of liquid crystal/dye mixture is deposited outside the        perimeter of the border sealant    -   A roller is used to bring the top and bottom substrates together        and roll-fill the active area inside the perimeter of the border        sealant with the liquid crystal/dye mixture    -   The border sealant is UV cured to form an edge seal

EXAMPLE 2 Single Roller

In another example, shown in FIG. 6, the bottom substrate may be placedonto and fixed to a moving plate 150 and a single roller (110′) used toroll-fill the cells 120. In this example, either the moving roller 110′can cause the movement of the plate and/or the bottom substrate indirection A, or the moving plate 150 moves the bottom substrate andcauses the roller to roll in direction B, pairing the substrates androll-filling the cell.

EXAMPLE 3 Double Rollers (Top and Bottom)

In this example (FIG. 7), a set of top and bottom rollers 200, 202 areused to mate or pair the top flexible substrate 204 to the bottomflexible substrate 206. A border sealant 208 is applied to the bottomsubstrate 206. The rollers 200, 202, pull the flexible substrates thoughthe rollers in the web direction A. While rolling, the depositedelectro-optic mixture 210 simultaneously fills the controlled gapcreated between the two substrates 204, 206, while they are beingpaired.

This method can be adopted in a continuous roll-to-roll type process.The amount of OEM deposited on the substrates need not be so carefullygauged as the process also works when more OEM is used, resulting in aquantity of EOM flowing over the border seal during the roll-fillingstep. This is an advantage over prior methods of manufacture, whichrequired deposition of a very precise amount of OEM required to fill thecell such that the cell would be completely filled but the bordersealant would only minimally touch the LC.

EXAMPLE 4 Double Roller (Left and Right)

In this example, a set of left and right rollers 250, 252, are used topair the flexible substrate 254 with flexible substrate 256 while movingthe substrates in a vertical downward direction (FIG. 8).

Essentially the top and bottom rollers from the previously describedmethod are now placed side by side. The difference is that in this newarrangement, the substrates 254, 256, come together from two differenthorizontal directions E and F, respectively. The rollers pull theflexible substrates though the rollers in the web direction G, which isvertically downwards. While rolling, the deposited EOM simultaneouslyfills the controlled gap created between the two substrates while theyare being paired, as described previously. This set-up would make iteasier to print or pattern any alignment layer on the substrates, and/orallow additional processing steps to be performed on one or both plasticsheets/substrates.

EXAMPLE 5

In another example, two rolls of substrate are each placed on rollers.Each roll is 3 mil PET from Mitsubishi plastics. The substrate rolls arepre-coated with a conductive layer, ITO, by Materion. The ITO coatedsubstrates are then coated with a polyimide alignment layer, 5661 fromNissan Chemicals. Shinshikyu EW plastic spheres, 6 micron in diameter(Hiko Industrial Ltd, Hong Kong) are mixed into the polyimide during thecoating process and are present in at least one of the substrate rolls.The rollers unwind the rolls of substrate during the roll-to-rollprocess. One unwound roll becomes the top substrate, the second becomesthe bottom substrate. The substrates move though the roll-to-rollprocess at a web speed from about 0.5 inches per second to about 10inches per second. Each substrate has a corresponding border sealantprinter. In this case these printers are rotary screen printers. Therotary screen printers print the border sealant, Loctite 3108, on eachof the active surfaces of the top and bottom substrate. Active surfacesare the surfaces that will be in contact with the EOM in the finishedcell. A rotary printer will print a border sealant at a height fromabout 5 microns to about 100 microns, preferably from about 5 microns toabout 40 microns. After rotary printing, EOM is deposited on the activesurface of the bottom substrate by a syringe and needle dispenser. TheEOM is a guest-host dichroic dye-liquid crystal mixture, AMI 577. A setof top and bottom lamination rollers mate the top and bottom substratestogether such that the top border sealant is aligned with the bottomborder sealant and the EOM makes contact with both top and bottom activesurfaces and though the roll-filling process, fills the entire interiorborder sealant area. The lamination rollers are configured to bepressure rollers that apply constant pressure across the substrateduring the lamination, or configured to be set-gap rollers where the toplamination roller is spaced at a set distance from the bottom laminationroller and allows the top and bottom substrates to mate withoutcompressing the controlled gap and spacers between the top and bottomsubstrate. The mated substrates are cured after lamination by UVradiation, heat, or a combination of UV and thermal cure. The curedsubstrates are then cut from the roll into sheets for additionalprocessing.

The invention claimed is:
 1. A method of producing a flexible cell unitenclosed by a border seal and filled with an electro-optic material, theflexible cell having a first and a second substrate separated by acontrolled distance, the method comprising: providing two continuoussheets of flexible plastic material to form the first and secondsubstrates, applying a plurality of unpatterned spacers within theflexible cell unit to the first substrate, the second substrate or both,depositing an electro-optic material on at least one substrate, whereinthe electro-optic material is non-discrete non-encapsulated,non-polymeric, and contains less than 1% polymerizable material; pairingthe first and second substrates while roll-filling the flexible cellwith the electro-optic material using one or more lamination rollers sothat the electro-optic material completely fills the controlled distancebetween the first and second substrates.
 2. The method of claim 1,wherein the method further comprises applying a border sealant on thefirst or second or both substrates before the roll filling step andcuring the border sealant to form the border seal after the roll-fillingstep.
 3. The method of claim 2, wherein the electro-optic material isdeposited on an area outside the perimeter of the border sealant, anarea inside the perimeter of the border sealant, or one or more areasboth inside and outside the perimeter of the border sealant.
 4. Themethod of claim 2, wherein during the roll-filling step, the ratio ofborder sealant viscosity to the electro-optic material viscosity isgreater than
 10. 5. The method of claim 2, wherein the method comprisesapplying multiple border sealants on the first, or the second, or bothsubstrates.
 6. The method of claim 1, wherein the method furthercomprises cutting the flexible cell unit from the two continuous sheetsof flexible plastic material using a mechanical die cutter, or a lasercutter, or a combination thereof.
 7. The method of claim 1, furthercomprising cutting or welding a shape to form a border seal after theroll-filling step using laser or heat or a combination of both.
 8. Themethod of claim 1, wherein the unpatterned spacers are integrated intothe electro-optic material that is deposited onto the at least onesusbstrate.
 9. The method of claim 1, wherein the method furthercomprises applying an alignment layer on the first substrate, the secondsubstrate, or both.
 10. The method of claim 9, wherein the methodfurther comprises depositing the unpatterned spacers within thealignment layer.
 11. The method of claim 1, wherein the method furthercomprises adding partition walls to one or both substrates.
 12. Themethod of claim 9, wherein the alignment layer is deposited by printingthe alignment layer on a selected active area of one or both the firstand second substrates.
 13. The method of claim 9, wherein the alignmentlayer is deposited by printing the alignment layer on the entire activearea of one or both the first and second substrates.
 14. The method ofclaim 1, wherein the flexible cell is an optical device having a hazevalue less than 8%.
 15. The method of claim 1, wherein the method isvacuum-less.
 16. The method of claim 1, wherein the unpatterned spacersare used to maintain a controlled distance of 3-100 μm in size.
 17. Themethod of claim 1, wherein the electro-optic material is selectivelydeposited in drops, lines or shapes on the first substrate.
 18. Themethod of claim 1, wherein the electro-optic material is a guest-hostdichroic dye-liquid crystal mixture.
 19. The method of claim 1, whereinthe flexible cell unit has an area greater than 30 cm².
 20. The methodof claim 1, wherein the flexible cell unit has a length greater than 10cm.
 21. A flexible cell unit comprising: first and second substratesseparated by a controlled distance maintained by unpatterned spacerswithin the flexible cell unit, filled with an electro-optic material andenclosed by a border seal, said flexible cell unit produced using amethod of manufacture comprising: providing two continuous sheets offlexible plastic material to form the first and second substrates,depositing the electro-optic material on at least one said substrate,wherein the electro-optic material is non-discrete non-encapsulated,non-polymeric, and contains less than 1% polymerizable material; androll-filling the cell by using one or more lamination rollers to pairthe first and second substrates to within the controlled distance ofeach other and filling said controlled distance with said electro-opticmaterial.
 22. The flexible cell unit of claim 21, wherein said method ofmanufacture further comprises applying a border sealant on the first orsecond or both substrates before the roll filling step and curing theborder sealant to form the border seal after the roll-filling step. 23.The flexible cell unit of claim 22, wherein said method of manufacturecomprises depositing the electro-optic material on an area outside theperimeter of the border sealant, an area inside the perimeter of theborder sealant, or one or more areas both inside and outside theperimeter of the border sealant.
 24. The flexible cell unit of claim 21,wherein said border seal is formed by applying a border sealant andwherein the ratio of border sealant viscosity to the electro-opticmaterial viscosity is greater than
 10. 25. The flexible cell unit ofclaim 22, wherein said method of manufacture comprises applying multipleborder sealants on the first, or the second, or both substrates.
 26. Theflexible cell unit of claim 21, wherein said method of manufacturefurther comprises cutting the flexible cell unit from the two continuoussheets of flexible plastic material using a mechanical die cutter, or alaser cutter, or a combination thereof.
 27. The flexible cell unit ofclaim 21, wherein said method of manufacture further comprising cuttinga shape to form the border seal and to separate the flexible cell unitfrom the two continuous sheets of flexible plastic after theroll-filling step.
 28. The flexible cell unit of claim 21, wherein saidmethod of manufacture further comprising welding a shape to form theborder seal after the roll-filling step using heat or laser or both. 29.The flexible cell unit of claim 21, wherein the unpatterned spacers areintegrated within the electro-optic material.
 30. The flexible cell unitof claim 21, wherein said method of manufacture further comprisesapplying an alignment layer on the first substrate, the secondsubstrate, or both.
 31. The flexible cell unit of claim 30, wherein theunpatterned spacers are within or part of the alignment layer.
 32. Theflexible cell unit of claim 21, wherein said method of manufacturefurther comprises adding partition walls to one or both substrates. 33.The flexible cell unit of claim 21, wherein the flexible cell is anoptical device having a haze value less than 8%.
 34. The flexible cellunit of claim 21, wherein said method of manufacture is vacuum-less. 35.The flexible cell unit of claim 21, wherein the unpatterned spacers areused to maintain a controlled distance of 3-100 μm in size.
 36. Theflexible cell unit of claim 21, wherein the electro-optic material isselectively deposited in drops, lines or shapes on the first substrate.37. The flexible cell unit of claim 21, wherein the electro-opticmaterial is a guest-host dichroic dye-liquid crystal mixture.
 38. Themethod of claim 21, wherein the flexible cell unit has an area greaterthan 30 cm².
 39. The method of claim 21, wherein the flexible cell unithas a length greater than 10 cm.
 40. A method of producing a flexiblecell unit enclosed by a border seal and filled with an electro-opticmaterial, the flexible cell unit having a first substrate and a secondsubstrate separated by a controlled distance maintained by a pluralityof unpatterned spacers within the flexible cell unit, the methodcomprising: providing two continuous sheets of flexible plastic materialas the first and second substrates, wherein the unpatterned spacers arepre-applied to at least one of the first and second substrates,depositing an electro-optic material on at least one substrate, whereinthe electro-optic material is non-discrete non-encapsulated,non-polymeric, and contains less than 1% polymerizable material; andpairing the first and second substrates while roll-filling the flexiblecell unit with the electro-optic material using one or more laminationrollers so that the electro-optic material completely fills thecontrolled distance between the first and second substrates.
 41. Themethod of claim 40, wherein the method further comprises applying aborder sealant on the first or second or both substrates before the rollfilling step and curing the border sealant to form the border seal afterthe roll-filling step.
 42. The method of claim 41, wherein theelectro-optic material is deposited on an area outside the perimeter ofthe border sealant, an area inside the perimeter of the border sealant,or one or more areas both inside and outside the perimeter of the bordersealant.
 43. The method of claim 41, wherein during the roll-fillingstep, the ratio of border sealant viscosity to the electro-opticmaterial viscosity is greater than
 10. 44. The method of claim 41,wherein the method comprises applying multiple border sealants on thefirst, or the second, or both substrates.
 45. The method of claim 40,wherein the method further comprises cutting the flexible cell unit fromthe two continuous sheets of flexible plastic material using amechanical die cutter, or a laser cutter, or a combination thereof. 46.The method of claim 40, further comprising cutting or welding a shape toform a border seal after the roll-filling step using laser or heat or acombination of both.
 47. The method of claim 40, wherein the methodfurther comprises applying an alignment layer on the first substrate,the second substrate, or both.
 48. The method of claim 40, wherein thepre-applied unpatterned spacers are within an alignment layer.
 49. Themethod of claim 40, wherein the method further comprises addingpartition walls to one or both substrates.
 50. The method of claim 40,wherein the flexible cell is an optical device having a haze value lessthan 8%.
 51. The method of claim 40, wherein the method is vacuum-less.52. The method of claim 40, wherein the unpatterned spacers arespherical and 3-100 μm in size.
 53. The method of claim 40, wherein theelectro-optic material is selectively deposited in drops, lines orshapes on the first substrate.
 54. The method of claim 40, wherein theelectro-optic material is a guest-host dichroic dye-liquid crystalmixture.
 55. The method of claim 40, wherein the flexible cell unit hasan area greater than 30 cm².
 56. The method of claim 40, wherein theflexible cell unit has a length greater than 10 cm.